fix(registry): drop wall-clock generated_at from registry.json to stop regen churn (age-9itj)

registry.json carried a wall-clock `generated_at` that generate-registry.sh rewrote on every `make regen-all`, so back-to-back regens were never byte-identical — it conflicted or re-noised at nearly every serial landing (cherry-pick conflicts on that line, idempotency proof-runs dirtying the tree, hand-reverting the pure-timestamp bump).

Remove the field from the body: registry.json is now a pure content-derived projection of its sources, matching the other generators (generate-context-map.sh / generate-skill-domain-map.sh already carry no timestamp). No consumer read the value — registry.go declares the field but never reads it, check mode already does del(.generated_at), and no schema/doc/jq/bats asserts it. Provenance for 'when generated' = git log on the file.

Verified: make regen-all twice -> registry.json byte-identical (sha256) + empty between-runs diff; make regen-check still reds on an un-regen'd skill body edit (codex-hash drift) and is green at rest; generate-registry.sh --check, validate-sku-catalog-drift.sh, 'ao registry list', and go build/vet/test (61 pass) all still work.

registry.json

@@ -1,6 +1,5 @@
 {
   "schema_version": 2,
-  "generated_at": "2026-07-02T13:09:42Z",
   "summary": {
     "skills": 63,
     "hooks": 0,

scripts/generate-registry.sh

@@ -536,9 +536,12 @@ build_cadence_recommendations() {
 # ─── Assemble ────────────────────────────────────────────────────────────────
 
 main() {
-  local generated_at
-  generated_at="$(date -u +%Y-%m-%dT%H:%M:%SZ)"
-
+  # No wall-clock stamp in the committed artifact: a `generated_at` timestamp
+  # made back-to-back regens non-byte-identical (rewrote every `make regen-all`),
+  # which collided/re-noised at nearly every serial landing. registry.json is now
+  # a pure content-derived projection of its sources — matching the other
+  # generators (generate-context-map.sh / generate-skill-domain-map.sh, which
+  # also carry no timestamp). "When was this generated" = git log on the file.
   local skills hooks knowledge_stores job_types schedules evals cli_commands cadence
   local ao_bin sku_block
 
@@ -579,7 +582,6 @@ main() {
   # capabilities/capability_summary).
   local registry
   registry=$(jq -n \
-    --arg generated_at "$generated_at" \
     --argjson skill_count "$skill_count" \
     --argjson hook_count "$hook_count" \
     --argjson store_count "$store_count" \
@@ -602,7 +604,6 @@ main() {
     --argjson workflow_count "$workflow_count" \
     '{
       schema_version: 2,
-      generated_at: $generated_at,
       summary: {
         skills: $skill_count,
         hooks: $hook_count,
@@ -639,7 +640,10 @@ main() {
         echo "FAIL: registry.json does not exist. Run: bash scripts/generate-registry.sh" >&2
         exit 1
       fi
-      # Compare ignoring generated_at timestamp
+      # generated_at was removed from the body (was wall-clock, caused churn);
+      # del(.generated_at) stays as a defensive no-op so an older committed
+      # registry.json that still carries the field still compares clean during
+      # rollout (and tolerates the field being reintroduced elsewhere).
       local current_no_ts new_no_ts
       current_no_ts=$(jq 'del(.generated_at)' "$OUTPUT")
       new_no_ts=$(echo "$registry" | jq 'del(.generated_at)')